Counting the Fish in the Sea

The 2010 US census workers had a tough job, but at least they were on land, counting residents with home addresses. 2010 was also the year a group of marine biologists completed a much tougher assignment: a global canvass of ocean residents who don’t fill out forms, live in some of the most remote places on the planet, and often move thousands of miles in a single year. The first study of its scope, the Census of Marine Life has added thousands of new species to the books, and has shown, in the words of project director Jesse Ausubel, that “the ocean’s even richer in diversity than anybody had known.”

The newly discovered Kiwa hirsuta, also known as the Yeti crab. Image courtesy of Chris Allen and the Encyclopedia of Life.

Census scientists collected over 6,000 new species, and have already described 1,200 of them in detail. They discovered deep-sea jellyfish, 500-year-old tubeworms, bejeweled copepods and isopods, and a hairy white crab that lives near sulfurous vents on the ocean floor. They found a mat of filamentous bacteria the size of Greece off the coast of Chile, and located a squid previously believed to have gone extinct in the Jurassic. The Census uncovered new life forms even in some of the world’s most studied and heavily trafficked ocean regions, said Ausubel, Census co-founder and program director at the Alfred P. Sloan Foundation, who described the results in a talk in Washington, DC last Thursday.

Each newly discovered species now has its own web page in the online Encyclopedia of Life, which will eventually catalog every known life form on Earth. Pages in the encyclopedia include physical descriptions of the species, scientific information like where the creature is found and how common it is, and, of course, color photos. “It’s like facebook,” Ausubel said. In addition, scientists gathered DNA from every creature found, new or not, for a project called the International Barcode of Life. The iBOL is a reference library made of segments of specific genes that are shared among many forms of life, but whose precise sequence varies in an identifiable way from species to species.

Scientists also learned that many familiar marine animals make long-distance trips across the ocean, “commuting like jetset businessmen” in Ausubel’s words. Census researchers attached acoustic tags to various creatures and released them; the tags then emitted sounds that were picked up by receivers on the ocean floor as the animals passed by. Scientists watched bluefin tuna swim from Mexico to Japan and back in a year, and tracked seals fishing from underwater mountains off the Antarctic coast. They monitored salmon swimming up the west coast of Canada, and learned that many of them don’t make it back to rivers to spawn the next year. And they used the tags to collect data beyond just the animals’ locations; for example, they enlisted leatherback turtles to collect ocean temperature readings during their journeys around the South Pacific. “Animals connect the ocean in incredible ways,” said Ausubel.

Surveying the astounding diversity of marine habitats—coastlines, continental shelves, deep-sea trenches and mountain ranges, the vast open ocean—required a correspondingly varied array of exploratory techniques: “a concerto of technologies,” said Ausubel. To explore the ocean surface and shallow waters, scientists worked from submarines, airplanes, and massive research vessels. For probing the deep ocean, they turned to robotic and remotely controlled vehicles that could operate at depth without risk to human life. In total, the project cost $650 million spread over a decade, and involved almost 3,000 scientists. “Marine biology hasn’t had a tradition of big science” like physics has, said Ausubel, but with the Census of Marine Life, that may be starting to change.

Although Ausubel noted that “extinction is rare in the ocean,” scientists found ample evidence of humans’ effects on life in the sea, few of them good. Overharvesting has depleted the populations of various fish, mammals, and reptiles since the time of the Romans, and in recent times has led to explosions of less desirable creatures, like jellyfish. Modern scourges like the huge floating garbage patches in the Atlantic and Pacific are also harming aquatic life, particularly island-nesting birds that are often found dead with plastic in their stomachs. But the greatest impacts may be yet to come, as humans increase shipping, oil drilling, and underwater communication, and as rising greenhouse gas emissions continue to warm the ocean and make it more acidic. The Census has given scientists a valuable baseline against which to measure future changes to the abundance and distribution of ocean dwellers.

Despite their impressive findings, marine biologists have just begun the hard part of counting every creature in the sea. They believe the ocean could contain a million or more undiscovered species, most of which are likely to be small, rare, and hard to find. And those are just the relatively well-studied multi-cellular ocean dwellers; the number of microbial species in the ocean is far larger, perhaps as many as a billion. Ausubel also noted that few people study most marine life forms, besides the well-known ones like fish and mammals (a hint to any young scientists out there searching for a specialty.)

The seas have long fascinated and mystified us. Over 60 years ago, Rachel Carson’s best-selling book The Sea Around Us told the public about the stunning discoveries in marine biology made possible by World War 2-era innovations in sonar and submarine technology. Since then we have learned much about what lives in the deep sea, and we now know the ocean floor is not barren but in fact teems with strange and wonderful life. But the Census of Marine Life also reaffirms the lure of the unknown that Carson described in her 1951 masterpiece: “We can only sense that in the deep and turbulent recesses of the sea are hidden mysteries far greater than any we have solved.”